Lithographic masks

For most activities in microtechnology, lithography (a technique in which a copy of the master sample is transferred on the surface of a solid material such as a wafer) is of particular importance. The pattern of a micron or nano chip is transferred on the substrate/substrate with the help of a process called lithography. First, the substrate is covered with a thin layer of light-sensitive organic material called photoresist. Then, the pattern is aligned with the substrate and is irradiated on the substrate using a light source such as Deep UV. Finally, the resulting image is displayed and inspected like a photographic film. The function of the mask is to selectively expose the photoresist layer that covers the surface of the wafer.

Mask made in Rasa company

A mask is made of a transparent glass such as fused silica, quartz or Sodalime glass (the material used in making laboratory slides) on which a thin layer of chromium is layered. Laminated chrome prevents light from passing through and is topped with a layer of photoresist (usually positive).

Parts of the photoresist are exposed by the mask writing device. By removing the exposed photoresist layer and dropping the mask into the chrome remover solution, parts of the chrome that are not protected by the photoresist are removed and the clear glass underneath is revealed. In this way, the light will pass through these parts in the shape of the pattern created by the chrome.

Wafer patterning process

Rasa company has the following services and activities in the field of preparing and making masks:

  • Preparation of raw masks with different dimensions (based on the order, for more information, call 021-64545437)
  • Create a pattern on the mask (to create a pattern, the software file of the mask with the conditions specified in this link must be prepared by the applicant and delivered to the laboratory. For more information, contact the supervisor of the laboratory in this link)
  • Mask design (if you are not interested in mask design, Rasa Company offers mask design service, for more information, contact the head of the laboratory in this link)